Both former Massachusetts governor Mitt Romney (R) and former senator Rick Santorum (R-Pa.) are blitzing Michigan today. Romney holds three events. He starts off in Rockford in western Michigan, then swings down to Albion, south of Lansing, and wraps up in Royal Oak just outside Detroit.

Santorum also holds three events, sweeping from east to west across the state. He begins the day in the Detroit suburb of Livonia, then heads west to Lansing, and ends in Kalamazoo in western Michigan.

The reason for the candidates’ focus on Michigan is pretty straightforward. If Romney loses the state – his home state and one that he won four years ago — it will deliver a major symbolic blow to his campaign.

If Santorum wins Michigan, it will give him a boost heading into Super Tuesday, and many Santorum supporters believe that a Wolverine State win would give their candidate enough momentum to claim victory in Ohio, another Rust Belt state, on March 6.

A key question to ponder: Who does Paul’s active campaign presence in the state hurt most? Is he more likely to draw votes away from Romney or from Santorum (who, like Paul, is one of the “non-Romneys” in the race)? Or are Paul’s voters a separate bunch entirely from those who would likely back either Santorum or Romney?

While Paul, Santorum and Romney campaign across the Wolverine State, former House speaker Newt Gingrich (R-Ga.) is elsewhere. He spends the day in Tennessee.